Early studies of penetrative RBC focused on the stability of the flows near the onset of convection [1]}, [2]}, [3]}, [4]}, [5]}. Recently, turbulent RBC of cold water near \(T_m\)  also attracted attention [6]}, [7]}, [8]}. In Ref. [6]},
the internal gravity wave excitation by convection was studied using two-dimensional (2D) direct numerical simulations (DNS).
In Ref. [7]}, convection in cold water was investigated by means of 2D and three-dimensional (3D) DNS. It was shown that for \(0\le \theta _m\lesssim 0.9\) , the mean central temperature \(\theta _c\) , the normalized Nusselt number \(Nu(\theta _m)/Nu(0)\) , and the normalized Reynolds number \(Re(\theta )/Re(0)\)  are almost independent of \(Ra\)  and thus to be claimed to be universal.
